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Tanker water markets (TWM) supply water services in many urban areas, including those unconnected to public infrastructures. Notwithstanding, they have been associated with outcomes in conflict with sustainability goals of water policy, e.g., through inequitable and unaffordable supply or by contributing to groundwater overexploitation. So far, the literature dedicated to TWM has primarily conducted case studies embedded in diverse local contexts, which impedes the comparison and transfer of insights. In this article, we systematically summarize existing empirical knowledge on TWM and assess to what extent normative claims about the impacts of TWM on sustainability goals are supported by evidence. We use the concept of sustainable access, which combines notions of what constitutes access to water and what characterizes sustainable supply of services. The available evidence suggests that TWM have two key functions in urban water systems: (1) They provide services at otherwise unavailable levels, particularly with respect to the temporal availability and spatial accessibility of the service, and (2) they extend access to areas without or with low-quality network supply, typically low-income communities on the fringe of cities. From the perspective of sustainable access, we find that TWM can provide high service levels and thus fill a specific gap in the landscape of urban water services. Due to comparatively high prices, however, it is unlikely that these services are affordable for all. The combination of heterogeneous access to cheaper (subsidized) piped water and marginal pricing in TWM results in allocation outcomes that are not coherent with existing notions of equitable access to water. However, there is little convincing evidence that TWM necessarily result in unsustainable water use. The literature indicates that urban water governance in the studied areas is frequently characterized by a lack of effective institutions, which impedes the regulation or formalization of TWM. 

Many private households spend considerable amounts of time accessing water, for instance by walking to and queuing at public access points, or by filling storage vessels at taps with low flow rates. This time has an opportunity cost, which can be substantial and may impact which water services and quantities of water households demand. In a novel form of diary study, we gathered detailed water consumption and time use data from 50 households in five informal settlements of the Indian metropolis Pune, accompanied by a household survey and in-depth interviews. With the data, we characterize water collection behaviors and assign monetary values to water procurement time. We statistically analyze the effects of time cost on consumed quantities in several two-level mixed-effect models. Household members in our sample spend up to several hours each day filling storage vessels, even if a private connection to the piped network is available. Average time cost amounted to the equivalent of 4.23–13.81% of monthly household cash income. Our analyses indicate that procurement time reduces quantitative water demand in a significant way. The households incurring the highest per-unit time cost consumed water quantities below minimum levels recommended for human health. This substantiates that time costs can impede access to water and are a relevant issue for water management and policy. 

Private households around the world use and combine multiple water sources, including diverse forms of market services and self-supply. The reasons for this have so far not been explained in a coherent framework, nor have the implications for water management and policy been sufficiently analyzed. Here, we examine how heterogeneity of water services, household co-production, and risks of provision influence household demand patterns. We apply an economic household production model that incorporates two water quality levels for different household activities to exemplary situations. We derive a number of explanations why households use and combine water services that expand the current state of research. Relevant findings include: (i) The diverse characteristics of available water services result in different time requirements for water procurement and varying degrees of suitability for household activities. (ii) Differences in the value placed on time can induce households to demand heterogeneous water services because these enable them to find a balance between using time and money to access water. (iii) Certain water services may be demanded because they function as insurance against both uncertain and unreliable supply. Our insights are relevant for water policy, in particular for developing and managing demand-responsive systems, and for the implementation and monitoring of normative goals for access to water. 

Large cities worldwide are increasingly suffering from a nexus of food, water, and energy supply challenges. This complex nexus can be analyzed with modern physico-economic system models. Only when practical knowledge from those affected, experts, and decision makers is incorporated alongside various other data sources, however, are the analyses suitable for policy advice. Here, we present a concept for “Sustainability Nexus Workshops” suitable for extracting and preparing relevant practical knowledge for nexus modeling and apply it to the case of Amman, Jordan. The experiences of the workshop participants show that, although water scarcity is the predominant resource problem in Jordan, there is a close connection between food, water, and energy as well as between resource supply and urbanization. To prevent the foreseeable significant degradation of water supply security, actions are needed across all nexus dimensions. The stakeholders demonstrate an awareness of this and suggest a variety of technical measures, policy solutions, and individual behavioral changes—often in combination. Improving the supply of food, water, and energy requires political and institutional reforms. In developing these, it must be borne in mind that the prevalent informal structures and illegal activities are both strategies for coping with nexus challenges and causes of them. 

Systems models of the Food–Water–Energy (FWE) nexus face a conceptual difficulty: the systematic integration of local stakeholder perspectives into a coherent framework for analysis. We present a novel procedure to co-produce and systematize the real-life complexity of stakeholder knowledge and forge it into a clear-cut set of challenges. These are clustered into the Pressure–State–Response (PSIR) framework, which ultimately guides the development of a conceptual systems model closely attuned to the needs of local stakeholders. We apply this approach to the case of the emerging megacity Pune and the Bhima basin in India. Through stakeholder workshops, involving 75 resource users and experts, we identified 22 individual challenges. They include exogenous pressures, such as climate change and urbanization, and endogenous pressures, such as agricultural groundwater over-abstraction and land use change. These pressures alter the Bhima basin’s system state, characterized by inefficient water and energy supply systems and regional scarcity. The consequent impacts on society encompass the inadequate provision with food, water, and energy and livelihood challenges for farmers in the basin. An evaluation of policy responses within the conceptual systems model shows the complex cause–effect interactions between nexus subsystems. One single response action, such as the promotion of solar farming, can affect multiple challenges. The resulting concise picture of the regional FWE system serves resource users, policymakers, and researchers to evaluate long-term policies within the context of the urban FWE system. While the presented results are specific to the case study, the approach can be transferred to any other FWE nexus system. 

The Hashemite Kingdom of Jordan is confronted with a severe freshwater crisis shaped by excess water demand and intermittent public supply. In Jordan’s capital and most populous city, Amman, the pervasive water shortage gave rise to private tanker water operations, which transport groundwater from wells in the vicinity of the city and sell it to urban consumers. These tanker water markets have received little attention in the literature up to date, particularly with regard to their relevance for commercial water users. This paper aims to empirically estimate the water demand of commercial establishments in Amman under public supply rationing and to assess to which extent tanker operations contribute to meeting commercial water needs. Building on a prior simulation model of residential water consumption, the results of three extensive surveys concerned with tanker water markets and various geographic data, we develop a spatial agent-based model of the water consumption behavior of commercial establishments in different sizes. According to our estimation, 35–45% of the overall water volume consumed by the commercial sector stems from tanker operations, depending on the season. We find that the local disparities in access to affordable network water, along with the dispersion of groundwater wells around the city, result in considerable spatial differences in tanker water consumption. The outcome of this analysis could be relevant for policy attempting to enhance freshwater sustainability in Jordan.